The present invention relates generally to the field of pumps.
The advantageous use of positive displacement pumps, designed to operate in a manner to produce a substantially constant delivery, has heretofore been generally recognized by the construction industry and particularly for the application of cement and plaster to building surfaces by means of spray nozzles which require a relative constant rate of delivery.
A number of different pumping arrangements have been designed and manufactured with a view to obtaining pumping apparatus which would produce a substantially constant delivery of the pumped material by the use of two pumping cylinders arranged to operate in a more or less master and slave manner.
One such prior art pumping apparatus is exemplified by the structure disclosed in the Bennett, et al. U.S. Pat. No. 3,172,363, issured Mar. 9, 1965. The structure of this patent provides two pumping units which are horizontally spaced apart and driven by separate and independent driving connections from the opposite overhanging ends of the main drive shaft.
Although the apparatus of this patent, as well as others of the prior art, is successful in that a substantially constant flow of material is produced, the heretofore known arrangements have a physical arrangement of the pumping units such that many problems arise, including excessive wear of bearings and other parts, lack of easy accessibility to valve parts for replacement, cleaning, and the like, absence of safety-features, lack of compactness, inability to operate dependably for long periods of time, as well as others which still await a successful solution.
Accordingly, the present invention is concerned more particularly with a new and improved design of pumping apparatus in which many of the inherent problems of the prior art structures have been solved. One important distinction of the pumping apparatus of the present invention over that of the usual prior art arrangement, resides in the placement of the pumping units in vertically spaced relation with one pumping unit being positioned adjacently above the other.
Such arrangement permits the use of a balanced compact driving connection with the driving shaft in which the shaft connected components may be supported between a pair of main bearings in a manner to equalize the loading distribution in a manner that is not possible in the prior art arrangements wherein the shaft components are supported on overhanging shaft ends having a bearing support on one side only.
Also, the vertical arrangement of the pumping units allows the use of an improved compact valving arrangement in which it is possible to take advantage of the force of gravity for assisting in the movement of the valves towards their closed seated positions.
It has also been known heretofore from U.S. Pat. No. 3,639,086, issued Feb. 1, 1972, to provide a hinged discharge spout for the pumped material from a concrete pumping apparatus. The usual practice is to provide such spouts with a manually operable wedge lock or securing lug for releasably retaining the spout in its connected position and against hinged movement to an open disconnected position. The use of such securing devices in the known pumping arrangements creates a potential hazard, since release of the lug permits the spout to be forceably swung to the disconnected position by the pressurized pumped material remaining in the spout and connected delivery lines, and such uncontrolled discharge of material presents a potential possibility of injury to attending personnel.
To overcome the above mentioned hazard, the present invention utilizes a releasable latch that may be initially operated to permit only a slight disconnected hinged opening, until the pressurized material is sufficiently relieved to permit safe hinged movement of the spout to its fully disconnected position.